Generally, a developer solution, for use in color photography, consists of a water solution of various components including p-phenylene diamine developing agent which is oxidized by the exposed silver halide to react with a coupler and form a dye.
Such components include an antioxidant(s), an alkalizing agent(s), a buffering agent(s), an optical brightener(s), a development modifier(s), as well as other known components, such as those described for example in Research Disclosure 17643, December 1978.
It is material to the user of the chemistry for color photographic processing that such water solutions of the p-phenylene diamine color developing agent and additional components be prepared from concentrated compositions easily mixed with water. Such concentrated compositions must also be stable in the various storage conditions. Since it is not possible to make a single concentrated composition of the developer solution as such (due to both solubility and stability problems), it has become normal practice in the art to divide and package it into various groups of components to be mixed in water and prepare the bath for use.
The stability problems are particularly critical with p-phenylene diamine color developing agents, which have the tendency to oxidize in storage. To prevent this aerial oxidation, sulfite compounds required for the ready-for-use developer have been added to the concentrate containing the developing agents. However, the addition of sulfite compounds results in a degradation of the developing agent. In U.S. Pat. No. 3,615,572, reissued on Oct. 1, 1974 as U.S. Pat. No. Re. 28,185, a method for reducing the degradation of the developing agent has beed described, which comprises keeping the concentrated aqueous solution at pH less than about 4, preferably less than 1, the molar ratio of the sulfite compound to color developing agent being between 0.08:1 and 1.5:1, preferably between 0.08:1 and 0.5:1. This method, while protecting p-phenylene diamine compounds against degradation, reduces the effectiveness of the protection against aerial oxidation (sulfite at low pH is rapidly decomposed giving rise to evolution of sulfur dioxide). In practice, further quantities of sulfite compounds are to be incorporated into another part of the composition, but this does not prevent oxidation during storage of the concentrated developer solution.